The addition of hydrazine compounds to silver halide photographic emulsions or development baths has been indicated, for example, in U.S. Pat. No. 3,730,727 (development baths in which ascorbic acid and hydrazine are used conjointly); U.S. Pat. No. 3,227,552 (where hydrazine is used as an auxiliary developing agent for obtaining direct positive color images); U.S. Pat. No. 3,386,831 (where the .beta.-monophenylhydrazides of aliphatic carboxylic acids are included as stabilizers for silver halide sensitive materials); and in U.S. Pat. No. 2,1419,975 and "The Theory of the Photographic Process", by Mees, third edition, page 281. These cases, particularly U.S. Pat. No. 2,419,975, indicate that high contrast negative images are obtained by the addition of hydrazine compounds.
U.S. Pat. No. 2,419,975 discloses that very high contrast photographic characteristics with gamma (.gamma.) values in excess of 10 can be obtained by adding hydrazine compounds to silver chlorobromide emulsions and developing the materials in development baths at a high pH, such as 12.8. But strongly alkaline development baths of a pH approaching 13 are very susceptible to aerial oxidation, are unstable, and are unable to withstand long term storage or use.
Photographic materials with ultra-high contrast, such that the value of gamma exceeds 10, are particularly useful for the photographic reproduction of continuous tone negative or positive dot images as used in the manufacture of printing plates and for the reproduction of line drawings. In the past, a gamma of more than 10 was achieved using methods of developing silver chlorobromide emulsions in which the silver chloride content exceeded 50 mol %, preferably 75 mol %, in hydroquinone development baths having an effective sulfite ion concentration of less than 0.1 mol/liter. With these methods, however, the sulfite ion concentration in the development bath is low resulting in development baths that are very unstable, and consequently unable to withstand storage for more than 3 days.
In addition, because these methods require the use of a silver chlorobromide emulsion, which has a comparatively high silver chloride content, it is impossible to realize high speeds.
For these reasons, there is a great need for ultra-high contrast photographic materials using high speed emulsions that can reproduce dot images and line drawings and can be developed in stable development baths.
The inventors disclosed silver halide photographic emulsions that provide very high contrast negative photographic characteristics using stable development baths in, for example, U.S. Pat. Nos. 4,224,401, 4,168,977, 4,243,739, 4,272,614 and 4,323,643, but the acylhydrazine compounds used therein are known to have some disadvantages. These conventional hydrazines produce nitrogen gas during development processing. This gas accumulates in the film and forms bubbles that adversely effect the photographic image. These hydrazine compounds also wash-out into the development processing baths where they adversely affect other photographic materials.
Furthermore, these conventional hydrazines must be used in large quantities in order to realize increased speed and contrast. In cases where an especially high speed is required necessitating conjoint use of other speed increasing techniques (for example, by increased chemical sensitization, increased grain size, or the addition of compounds that enhance sensitization such as those disclosed in U.S. Pat. Nos. 4,272,606 and 4,241,164) then, in general, an increase in speed with the passage of time on storage and increased fogging are liable to occur.
Hence, compounds, a small amount of which will give rise to the following, are desirable: less bubble formation and wash-out into the development bath; high stability with the passage of time; and very high contrast.
The acylhydrazine derivatives disclosed in EP 217,310, JP-A-62-178246 and JP-A-62-180361 were developed with a view to overcoming the problems indicated above, but these compounds do not have sufficient activity as nucleating agents to enable the pH of the processing baths to be reduced to raise the stability of development processing baths (which is to say, to prevent the deterioration of the developing agent) or to enable the development processing time to be shortened. (The term "JP-A" as used herein signifies an "unexamined published Japanese patent application".)
Furthermore, it has been disclosed in U.S. Pat. Nos. 4,385,108, 4,269,929 and 4,243,739 that very high contrast negative gradation photographic properties can be realized using hydrazines which have substituent groups which are readily adsorbed on silver halide grains, but those of the hydrazine compounds which have the adsorbing groups cited in the aforementioned publications present a problem in that they lead to desensitization with the passage of time on storage.